Glass joint body and method of manufacturing the same

ABSTRACT

In order to improve the reliability of a glass joint body, a first ceramic member and a second ceramic member are connected by using (a) glass consisting of 10˜65 wt % of SiO 2 , 30 wt % or less of Na 2  O, and the balance of B 2  O 3  and Al 2  O 3 , (b) glass including less than 10 wt % of SiO 2 , and 30˜80 wt % of B 2  O 3 , (c) glass including substantially none of SiO 2 , and 30˜80 wt % of B 2  O 3 , or (d) glass consisting of 10˜65 wt % of SiO 2 , 20 wt % or less of Na 2  O, 30 wt % or less of Al 2  O 3 , 20 wt % or less of MgO, and the balance of B 2  O 3 .

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to glass joint bodies which are exposed tocorrosive substances, and especially relates to glass joint bodies to beused for a connection between B alumina and insulation ceramics inAlkali Metal Thermo-Electric Converters (AMTEC) or a secondary cell tobe used in high temperatures such as a sodium-sulfur cell. The presentinvention also relates to a method of manufacturing the glass jointbodies mentioned above.

2. Related Art Statement

Usually, as for one example of glass joint bodies which are exposed incorrosive substances, there is known a sodium-sulfur cell or AlkaliMetal Thermo-Electric Converter.

The sodium-sulfur cells are high temperature type secondary cells whichoperate at 300° C.˜350° C. and include metallic sodium as a cathodeactive material, sulfur and/or sodium polysulfide as an anode activematerial, a sodium ion conductive ceramic as a solid electrolyte, and ametal container. The structure of a typical sodium sulfur cell is shownin FIG. 1.

In FIG. 1, the numeral 1 is a beta alumina tube, 2 is a metal containerfunctioning as an anode, 3 is a sulfur or sodium polysulfide, 4 is ametal container functioning as a cathode, 5 is sodium, 6 is an insulatorsuch as α-alumina, 7 is a metal lid, 8 is a welded portion, and 9 is aconjunction glass for connecting the beta alumina tube 1 and theinsulator 6. As for the beta alumina material forming the beta aluminatube 1, use is made of β"-alumina, β-alumina, and a mixture of both, orthe like.

Processes for manufacturing the above-described sodium-sulfur cellsgenerally comprise the steps of: bonding the open end periphery of thebeta alumina tube 1 with the ring insulator 6 made of α-alumina by meansof glass or the like; bonding the ring insulator 6 supporting the betaalumina tube 1 with the metal containers 2 and 4 by a solid phasereaction or the like at a high temperature under pressure; supplying thesodium 5 and the sulfur or sodium polysulfide 3 into the metalcontainers 4 and 2 respectively; and hermetically closing the metalcontainers 4 and 2 with lids 7 and 8 by means of welding to provide acell.

In the sodium-sulfur cells mentioned above, the conjunction glass 9arranged between the beta alumina tube 1 and the insulator 6 made ofα-alumina and the like is corroded by the sodium, and consequently alife of the sodium-sulfur cell is decreased. To eliminate the drawbackmentioned above, a conjunction glass having good durability againstsodium corrosion consisting of 1 wt % alkali earth metal oxides or less,SiO₂ : 65˜75 wt. %, B₂ O₃ : 10˜25 wt %, and the balance of Al₂ O₃ andalkali metal oxides is disclosed in Japanese Patent Laid-OpenPublication No. 1-54672.

The conjunction glass having the composition mentioned above has gooddurability against sodium corrosion as compared with known silicateglass and boron silicate glass, but does not show a sufficientdurability against sodium corrosion as yet. Therefore, the conjunctionglass mentioned above is also corroded by the sodium and thus there is adrawback in that a life of the sodium-sulfur cell is also decreased.

SUMMARY OF THE INVENTION

An object of the invention is to eliminate the drawbacks mentioned aboveand to provide a glass joint body having a reliable glass joint portionand a method of producing the glass joint body mentioned above.

According to a first aspect of the invention, a glass joint bodycomprises a first ceramic member and a second ceramic member which areconnected by a glass consisting of 10˜65 wt % of SiO₂, 30 wt % or lessof Na₂ O, and the balance of B₂ O₃ and Al₂ O₃.

According to a second aspect of the invention, a glass joint bodycomprises a first ceramic member and a second ceramic member which areconnected by a glass including less than 10 wt % of SiO₂, and 30˜80 wt %of B₂ O₃.

According to a third aspect of the invention, a glass joint bodycomprises a first ceramic member and a second ceramic member which areconnected by a glass including substantially no SiO₂, and 30˜80 wt % ofB₂ O₃.

According to a fourth aspect of the invention, a glass joint bodycomprises a first ceramic member and a second ceramic member which areconnected by a glass consisting of 10˜65 wt % of SiO₂, 20 wt % or lessof Na₂ O, 30 wt % or less of Al₂ O₃, 20 wt % or less of MgO, and thebalance of B₂ O₃.

According to a fifth aspect of the invention, a method of manufacturinga glass joint body comprises the steps of preparing (a) glass consistingof 10˜65 wt % of SiO₂, 30 wt % or less of Na₂ O, and the balance of B₂O₃ and Al₂ O₃, (b) glass including less than 10 wt % of SiO₂, and 30˜80wt % of B₂ O₃, (c) glass including substantially no SiO₂, and 30˜80 wt %of B₂ O₃, or (d) glass consisting of 10˜65 wt % of SiO₂, 20 wt % or lessof Na₂ O, 30 wt % or less of Al₂ O₃, 20 wt % or less of MgO, and thebalance of B₂ O₃ ; and connecting a first ceramic member and a secondceramic member by using the thus prepared glass.

In the structure of the first aspect of the invention, since theconjunction glass consisting of SiO₂ : 10˜65 wt %, Na₂ O: 30 wt % orless, and the balance of B₂ O₃ and Al₂ O₃ is used for a connectionbetween two ceramic members, a corrosion rate due to sodium can bereduced, and thus reliability of the glass joint portion can beimproved. Therefore, the life of the sodium-sulfur cell can beincreased.

In the glass composition of the first aspect of the invention, thereasons for limiting an amount of SiO₂ to 10˜65 wt % and for limiting anamount of Na₂ O to 30 wt % or less are as follows. If an amount of SiO₂is less than 10 wt %, a thermal expansion coefficient is increased andresidual stress due to the connection becomes larger, and thus cracksare generated when a connection operation is performed. Moreover, if anamount of SiO₂ is more than 65 wt %, a corrosion rate due to Na becomesextremely high and thus cracks are generated in a short time aftercontacting Na. Further, if an amount of Na₂ O is more than 30 wt %, athermal expansion coefficient is increased and a residual stress due tothe connection becomes larger, and thus cracks are generated when aconnection operation is performed.

Furthermore, it is preferred to limit an amount of SiO₂ to 20˜60 wt %and more preferably 30˜50 wt %. Moreover, it is preferred to limit anamount of NazO to 20 wt % or less and more preferably 15 wt % or less.Further, it is preferred to limit a total amount of alkali metal oxidesand alkali earth metal oxides other than Na₂ O to 0.5 wt % or less.

In the structures of the second and third aspects of the invention,since the conjunction glass including less than 10 wt % or substantiallyno SiO₂ and 30˜80 wt % of B₂ O₃ is used for a connection between twoceramic members, a corrosion rate due to sodium can be controlled to beslow, and thus a reliability of the glass joint portion can be improved.Therefore, a life of the sodium-sulfur cell or the Alkali MetalThermo-Electric Converter can be increased.

In the glass composition of the second aspect of the invention, thereason for limiting an amount of SiO₂ to less than 10 wt % is asfollows. If an amount of SiO₂ is 10 wt % or more, durability againstsodium corrosion of the glass is decreased, and thus cracks aregenerated in the glass portion due to corrosion. Moreover, in the glasscomposition of the third aspect of the invention, the reason forlimiting an amount of SiO₂ to substantially zero is to obtain a glasswhich is not corroded at all by sodium. Moreover, in the glasscompositions of the second and third aspects of the invention, thereason for limiting an amount of B₂ O₃ to 30˜80 wt % is as follows. Ifan amount of B₂ O₃ is less than 30 wt %, it is not possible to generatea glassy state. Moreover, if an amount of B₂ O₃ is more than 80 wt %,the glass is easily deteriorated due to water absorption. Further, it ispreferred to limit an amount of Na₂ O to 30 wt % or less, because athermal expansion coefficient is increased and cracks are easilygenerated during connection operations if an amount of Na₂ O is morethan 30 wt %.

Moreover, as for an amount of Al₂ O₃ and an amount of MgO, it ispreferred to limit an amount of Al₂ O₃ to 35 wt % or less and an amountof MgO to 40 wt % or less. This is amount of MgO is more than 40 wt %, acantilever flexural strength of the glass joint body is largelydecreased. Further, it is preferred to further limit an amount of Al₂ O₃to 13˜28 wt % and an amount of MgO to 12˜25 wt %, because the cantileverflexural strength thereof is increased.

In the structures of the fourth aspect of the invention, since theconjunction glass consisting of 10˜65 wt % of SiO₂, 20 wt % of Na₂ O orless, 30 wt % of Al₂ O₃ or less, 20 wt % of MgO or less, and theremainder of B₂ O₃ is used for a connection between two ceramic members,a corrosion rate due to sodium can be reduced, and thus a reliability ofthe glass joint portion can be improved. Therefore, a life of thesodium-sulfur cell or the Alkali Metal Thermo-Electric Converter can beincreased.

In the glass composition of the fourth aspect of the invention, thereasons for limiting an amount of SiO₂ to 10˜65 wt % and for limiting anamount of Na₂ O to 20 wt % or less are as follows. If an amount of SiO₂is less than 10 wt %, a thermal expansion coefficient is increased and aresidual stress due to the connection becomes larger, and thus cracksare generated when a connection operation is performed. Moreover, if anamount of SiO₂ is more than 65 wt %, corrosion generation due to sodiumbecomes extremely high, and thus cracks are generated in a short timeafter contacting Na. Further, if an amount of Na₂ O is more than 20 wt%, a thermal expansion coefficient is increased and a residual stressdue to the connection becomes larger, and thus cracks are generated whena connection operation is performed. Furthermore, it is preferred tolimit an amount of SiO₂ as 20˜40 wt %.

Moreover, the reason for limiting an amount of Al₂ O₃ to 30 wt % or lessand for limiting an amount of MgO to 20 wt % or less is that, if anamount of Al₂ O₃ is more than 30 wt % or an amount of MgO is more than20 wt %, the glass crystallizes and cracks are generated.

Further, preferable methods of connecting two ceramic members are (1) amethod comprising the steps of arranging a glass frit between an alphaalumina ceramic and a beta alumina ceramic, and melting the glass byheat to connect the alpha alumina ceramic and the beta alumina ceramicby reacting the glass and the alpha alumina ceramic and also by reactingthe glass and the beta alumina ceramic, or (2) a method comprising thesteps of arranging a glass block on a space between an alpha aluminaceramic and beta alumina ceramic, melting the glass block by heat sothat the glass block flows into the space, and connecting the alphaalumina ceramic and the beta alumina ceramic by reacting the glass andthe alpha alumina ceramic and also by reacting the glass and the betaalumina ceramic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a sodium sulfur cell, as oneembodiment of a glass joint body according to the invention;

FIG. 2 is a schematic view illustrating an Alkali Metal Thermo-ElectricConverter, as another embodiment of a glass joint body according to theinvention;

FIG. 3 is a cross sectional view depicting one embodiment of a specimento which an anti-sodium test is performed;

FIG. 4 is a cross sectional view showing another embodiment of aspecimen to which an anti-sodium test is performed; and

FIG. 5 is a cross sectional view for explaining a cantilever bendingtest.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic view showing one embodiment of a glass joint bodyaccording to the invention. In FIG. 1, the present invention is appliedto a sodium-sulfur cell, and a construction of the sodium-sulfur cell isexplained before, so that the explanation thereof is not repeated here.In this embodiment, as for the conjunction glass 9, use is made of (a)glass consisting of 10˜65 wt % of SiO₂, 30 wt % or less of Na₂ O, andthe balance of B₂ O₃ and Al₂ O₃, (b) glass including less than 10 wt %of SiO₂, and 30˜80 wt % of B₂ O₃, (c) glass including substantially noSiO₂, and 30˜80 wt % of B₂ O₃, or (d) glass consisting of 10˜65 wt % ofSiO₂, 20 wt % or less of Na₂ O, 30 wt % or less of Al₂ O₃, 20 wt % orless of MgO and the balance of B₂ O₃.

FIG. 2 is a schematic view showing another embodiment of a glass jointbody according to the invention. In FIG. 2, the present invention isapplied to a thermoelectric converting apparatus. In the Alkali MetalThermo-Electric Converter shown in FIG. 2, heat energy is directlyconverted into electrical energy to generate electricity by utilizing abeta alumina solid electrolyte through which a sodium ion is easilymoved. In this embodiment, 11 is a stainless container, 12 is aninsulator made of α-alumina fixed to the stainless container 11, 13 is abeta alumina tube, 14 is a conjunction glass for connecting theinsulator 12 made of α-alumina and the beta alumina tube 13, 15 is aheater for heating sodium supplied into the beta alumina tube 13, 16 isan Mo porous electrode formed on an outer surface of the beta aluminatube 13, 17 is a pipe for supplying sodium in the stainless container 11into the beta alumina tube 13, 18 is an electromagnetic pump for movingsodium in the pipe 17, and 19-1 and 19-2 are electrodes for outputterminals. Also in this embodiment, it is necessary to use theconjunction glass 14 having a composition (a), (b), (c), or (d)mentioned above.

In the thermoelectric converting apparatus mentioned above, sodiumsupplied in the beta alumina tube 13 is heated by the heater 15 and ismoved to the Mo porous electrode 16 by means of ion conductivity, sothat an output current flows between the electrodes 19-1 and 19-2.Moreover, sodium moved to the Mo porous electrode 16 by means of ionconductivity is vaporized from the Mo porous electrode 16, and isliquefied on an inner surface of the stainless container 17, which ismaintained at low temperatures. In this manner, sodium is circulated inthe thermoelectric converting apparatus.

Hereinafter, actual embodiments will be explained.

EXAMPLE 1

In order to examine a connection state of a glass joint specimen anddurability against sodium corrosion of a glass having variouscompositions in the first aspect of the invention, the following testswere performed.

At first, glass frits having various chemical compositions as shown inTable 1 were prepared by measuring respective raw materials by means ofan electronic balance, mixing and crushing the raw materials in a mortarmade of alumina by using a pestle, melting the mixed and crushed rawmaterials at 1600° C. in a platinum crucible, and dropping the meltedraw materials into water. In order to make properties of the glassuniform, the thus prepared glass frits were further crushed in a mortarmade of alumina by using an alumina pestle, and were re-melted at 1600°C. in a crucible made of platinum. After that, the thus re-melted glasswas dropped into water, and the cooled glass was further crushed in amortar made of alumina by using an alumina pestle to obtain glass fritsfor a connection.

By using the thus obtained glass frits, an alpha alumina circular plate31 having a diameter of 40 mm and a thickness of 5 mm was connected to abeta alumina tube 32 having an outer diameter of 20.0 mm and an innerdiameter of 17.5 mm at 1000° C. to obtain a glass joint specimen, asshown in FIG. 3. Then, the glass joint specimen was gradually cooledfrom 800° C. to 300° C. at a cooling rate of 0.5 C/min to eliminatestresses. After that, the thus formed glass joint specimen was immersedin sodium at 450° C. under N₂ atmosphere every 100 hours, and sodium waseliminated by using methanol. Then, crack generation was examined byusing fluorescent penetrant inspection every 100 hours. The results andthe chemical compositions of the conjunction glasses used in thisexample 1 are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                               Chemical composition                                                          (wt %)          Crack generation                                       Specimen No.                                                                           SiO.sub.2                                                                            Na.sub.2 O                                                                            B.sub.2 O.sub.3                                                                    Al.sub.2 O.sub.3                                                                    time (hr)                                  ______________________________________                                        present                                                                       invention                                                                     1        64.0   8.0     13.0 15.0    500                                      2        60.0   8.0     17.0 15.0    800                                      3        50.0   8.0     27.0 15.0  >1000                                      4        40.0   8.0     37.0 15.0  >1000                                      5        30.0   8.0     47.0 15.0  >1000                                      6        20.0   8.0     57.0 15.0   1000                                      7        10.0   10.0    55.0 25.0    600                                      8        50.0   3.0     30.0 17.0  >1000                                      9        50.0   15.0    20.0 15.0  >1000                                      10       50.0   20.0    15.0 15.0    900                                      11       50.0   30.0    10.0 10.0    600                                      12       50.0   8.0     30.0 12.0  >1000                                      13       50.0   9.0     29.0  2.0  >1000                                      comparative                                                                   example                                                                       14       70.0   8.0     12.0 10.0    100                                      15        8.0   8.0     70.0 14.0  crack generation                                                              during connection                          16       50.0   35.0    10.0  5.0  crack generation                                                              during connection                          ______________________________________                                    

From the results shown in Table 1, it is understood that specimen Nos.1˜13 of the first aspect of the invention show good durability againstsodium corrosion since cracks are not generated at least for 400 hours.However, specimen No. 18 of the comparative example can not endure formore than 100 hours, and specimen Nos. 15 and 16 are cracked when theconnection operation is performed. The reason for such crack generationduring the connection operation is that a thermal expansion coefficientof the glass is not suitable for beta alumina or alpha alumina.

EXAMPLE 2

A charge-discharge test was performed with respect to a NaS cell usingthe glass joint body of the first aspect of the invention. That is tosay, with respect to the sodium-sulfur cells wherein the beta aluminatube and the insulator made of alpha-alumina are connected as shown inFIG. 1 by using glasses of the specimen Nos. 1˜13 in example 1, thecharge-discharge test was performed under a temperature of 350° C. and acurrent density of 100 mA/cm². As a result, all of the sodium-sulfurcells endured at least 1000 cycles.

EXAMPLE 3

In order to examine a connection state of a glass joint specimen anddurability against sodium corrosion of a glass having variouscompositions in the second and third aspects of the invention, thefollowing tests were performed.

At first, glass frits having various chemical compositions as shown inTable 2 were prepared by measuring respective raw materials by means ofan electric balance, mixing and crushing the raw materials in a mortarmade of alumina by using an alumina pestle, melting the mixed andcrushed raw materials at 1200°˜1600° C. in a platinum crucible, anddropping the melted raw materials into water. In order to makeproperties of the glass uniform, the thus prepared glass frits werefurther crushed in a mortar made of alumina by using an alumina pestle,and were re-melted at the same temperature as that of the above meltingoperation in a crucible made of platinum. After that, the thus remeltedglass was dropped into water, and the cooled glass was further crushedin a mortar made of alumina by using a alumina pestle to obtain glassfrits for a connection.

By using the thus obtained glass frits, an α alumina ring 42 having adiameter of 32 mm and a beta alumina circular plate 43 having a diameterof 25 mm and a thickness of 3 mm were connected with each other at800°˜1000° C. to obtain a glass joint specimen as shown in FIG. 4. Then,the glass joint specimen was gradually cooled from 800° C. to 300° C. ata cooling rate of 0.5° C./min to eliminate stresses. After that, thethus formed glass joint specimen was immersed in sodium at 450° C. underN₂ atmosphere every 100 hours, and sodium was eliminated by usingmethanol. Then, crack generation was examined by using fluorescentpenetrant inspection every 100 hours. Moreover, generation of a coloredlayer was also examined by observing a cross section of the glass jointspecimen by means of an optical microscope. The results and the chemicalcompositions of the conjunction glasses used in example 3 are shown inTable 2. It should be noted that, in Table 2, SiO₂ <1.0 wt % representsthe conjunction glass including substantially no SiO₂.

                                      TABLE 2                                     __________________________________________________________________________                                              Crack                                                                         generation                                                                           Generation                          Chemical composition (wt %)        time   of colored                   Specimen No.                                                                         SiO.sub.2                                                                        B.sub.2 O.sub.3                                                                  Na.sub.2 O                                                                        Al.sub.2 O.sub.3                                                                  TiO.sub.2                                                                        MgO                                                                              ZrO.sub.2                                                                         Ta.sub.2 O.sub.5                                                                  La.sub.2 O.sub.3                                                                  Y.sub.2 O.sub.3                                                                  (hr)   layer                        __________________________________________________________________________    present                                                                       invention                                                                      1      9.0                                                                             56.0                                                                             20.0                                                                              15.0                     >1000  existent                      2      5.0                                                                             65.0                                                                             17.0                                                                              13.0                     >1000  existent                      3     <1.0                                                                             68.0                                                                             18.0                                                                              14.0                     >1000  none                          4     <1.0                                                                             80.0                                                                              7.0                                                                              13.0                     >1000  none                          5     <1.0                                                                             65.0                                                                              7.0                                                                              28.0                     >1000  none                          6     <1.0                                                                             72.0                                                                             25.0    3.0                  >1000  none                          7     < 1.0                                                                            61.0                                                                             27.0    12.0                 >1000  none                          8     <1.0                                                                             58.0   23.0   19.0              >1000  none                          9     <1.0                                                                             50.0   36.0   14.0              >1000  none                         10     <1.0                                                                             65.0   16.0   19.0              >1000  none                         11     <1.0                                                                             61.2   16.3   22.5              >1000  none                         12     <1.0                                                                             62.2   22.8   15.0              >1000  none                         13     <1.0                                                                             43.0   32.0   25.0              >1000  none                         14     <1.0                                                                             50.0   17.0   33.0              >1000  none                         15     <1.0                                                                             68.0    9.0   23.0              >1000  none                         16     <1.0                                                                             57.0   17.0   26.0              >1000  none                         17     <1.0                                                                             67.8          32.2              >1000  none                         18     <1.0                                                                             66.6   27.9    5.5              >1000  none                         19     <1.0                                                                             40.7   25.6   33.7              >1000  none                         20     < 1.0                                                                            45.4   25.0   29.6              >1000  none                         21     <1.0                                                                             62.2   22.8   15.0              >1000  none                         22     <1.0                                                                             46.0   12.0   42.0              >1000  none                         23     <1.0                                                                             50.0   36.0   14.0              >1000  none                         24     <1.0                                                                             59.0   38.0   12.0              >1000  none                         25     <1.0                                                                             62.0                                                                             16.0                                                                              13.0    9.0              >1000  none                         26     <1.0                                                                             53.0                                                                              9.0                                                                              21.0   17.0              >1000  none                         27     <1.0                                                                             65.0                                                                             17.0                                                                              14.0                                                                              4.0                  >1000  none                         28     <1.0                                                                             68.0                                                                             24.0                                                                               5.0                                                                              3.0                  >1000  none                         29     <1.0                                                                             40.0   29.0              31.0   >1000  none                         30     <1.0                                                                             65.0                                                                             10.0                                                                              20.0      5.0            >1000  none                         31     <1.0                                                                             40.0   26.0              30.0                                                                              4.0                                                                              >1000  none                         32     <1.0                                                                             30.0                                                                              8.0                                                                              17.0          45.0       >1000  none                         comparative                                                                   example                                                                       33      15.0                                                                            45.0                                                                             23.0                                                                              17.0                       700  existent                     34      26.0 36.0    38.0                 crack genera-                                                                 tion in case                                                                  of connection                       35     <1.0                                                                             24.0                                                                             12.0                                                                              20.0              44.0   poor glass                                                                    generation                          36     <1.0                                                                             35.0                                                                              3.0                                                                              27.0                     crack genera-                                                                 tion after                                                                    3 days from                                                                   connection                          __________________________________________________________________________

From the results shown in Table 2, it is understood that specimen Nos.1˜32 of the second and third aspects of the invention show gooddurability against sodium corrosion since cracks are not generated atleast for 5 hours, but specimen Nos. 33˜36 of the comparative examplecan not endure for 1000 hours and do not show sufficient durabilityagainst sodium corrosion since cracks are generated. Moreover, among thespecimens according to the invention, specimen Nos. 1 and 2, to whichless than 10 wt % of SiO₂ is added positively, generate no cracks for100 hours but have colored layers due to corrosion. Contrary to this,the specimen Nos. 3˜32, to which substantially no SiO₂ is included,generate no cracks and no colored layers, and show better durabilityagainst sodium corrosion than those of specimen Nos. 1 and 2.

EXAMPLE 4

A charge-discharge test was performed with respect to a NaS cell usingthe glass joint body of the second and third aspects of the invention.That is to say, with respect to the sodium-sulfur cells wherein the betaalumina and the alpha alumina are connected as shown in FIG. 2 by usingglasses of specimen Nos. 1˜32 in example 3, the charge-discharge testwas performed under a temperature of 350° C. and a current density of150 mA/cm². As a result, all the sodium-sulfur cells endured at least1000 cycles.

EXAMPLE 5

A cantilever bending test was performed with respect to a glass jointspecimen using the glasses of specimen Nos. 1˜21 shown in Table 3. Thatis to say, with respect to the glass joint specimen shown in FIG. 5wherein a beta alumina tube 52 having an inner diameter of 20 mm and athickness of 2 mm and an α-alumina ring 53 having an outer diameter of35 mm are connected by using the glass mentioned above, a load P isapplied at a position 200 mm apart from a connection portion of the betaalumina tube 52. Then, a load when the beta alumina tube 52 is broken ismeasured as a break load. The results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Specimen                                                                             Chemical composition (wt %)                                                                           Break load                                     No.    SiO.sub.2                                                                            B.sub.2 O.sub.3                                                                      Na.sub.2 O                                                                          Al.sub.2 O.sub.3                                                                    MgO  TiO.sub.2                                                                          P (Kgf)                            ______________________________________                                         1     <1.0   43.0         32.0  25.0      31.0                                2     <1.0   50.0         17.0  33.0      32.5                                3     <1.0   68.0          9.0  23.0      30.0                                4     <1.0   58.0         23.0  19.0      36.5                                5     <1.0   65.0    3.0  15.0  17.0      30.0                                6     <1.0   65.0         16.0  19.0      38.0                                7     <1.0   61.2         22.8  15.0      39.5                                8     <1.0   62.2         10.3  22.5      37.0                                9     <1.0   57.0         17.0  20.0      29.5                               10     <1.0   67.8               32.2      28.0                               11     <1.0   66.6         27.9   5.5      31.0                               12     <1.0   40.7         22.6  33.7      31.0                               13     <1.0   45.4         25.0  29.6      29.5                               14     <1.0   62.2         22.8  15.0      30.0                               15     <1.0   46.0         12.0  42.0      23.0                               16     <1.0   50.0         36.0  14.0      18.5                               17     <1.0   59.0         38.0  12.0      20.0                               18     <1.0   68.0   18.0  14.0            28.0                               19     <1.0   62.0   16.0  13.0   9.0      30.5                               20     <1.0   61.0         27.0       12.0 29.0                               21     <1.0   65.0   17.0  14.0        4.0 29.5                               ______________________________________                                    

From the results shown in Table 3, among the glasses according to thesecond and third aspects of the invention, specimen Nos. 16 and 17 inwhich 30 wt % or more of Al₂ O₃ is included and specimen No. 15 in which40 wt % or more of MgO is included show small break loads P as comparedwith the other specimens. Moreover, the specimen Nos. 4, 6, 7, 8 inwhich 13˜28 wt % of Al₂ O₃ and 12˜25 wt % of MgO are included show largebreak loads P as compared with the other specimens. It should be notedthat, among the specimens including substantially no SiO₂, there is nodifference in durability against sodium corrosion.

EXAMPLE 6

In order to examine a connection state of a glass joint specimen anddurability against sodium corrosion of a glass having variouscompositions in the fourth aspect of the invention, the following testswere performed.

At first, glass frits having various chemical compositions as shown inTable 4 were prepared by measuring respective raw materials by means ofan electric balance, mixing and crushing the raw materials in a mortarmade of alumina, melting the mixed and crushed raw materials at 1400° C.in a platinum crucible, casting the melted raw materials into a metalsaucer whose inner surface is spread by carbon paste to effect a rapidcooling, and crushing the cooled glass. In order to make properties ofthe glass uniform, the thus prepared glass frits were further crushed ina mortar made of alumina by using an alumina pestle, and were remeltedat 1400° C. in a crucible made of platinum. After that, the thusre-melted glass was rapidly cooled, and the cooled glass was furthercrushed in a mortar made of alumina by using an alumina pestle to obtainglass frits for a connection.

By using the thus obtained glass frits, an alpha alumina circular plate31 having a diameter of 40 mm and a thickness of 5 mm was connected to abeta alumina tube 32 having an outer diameter of 20.0 mm and an innerdiameter of 17.5 mm at 1000° C. to obtain a glass joint specimen, asshown in FIG. 3. Then, the glass joint specimen was gradually cooledfrom 700° C. to 300° C. at a cooling rate of 0.5° C./min to eliminatestresses. After that, the thus formed glass specimen was immersed insodium at 450° C. under N₂ atmosphere every 100 hours, and sodium wasexamined by using methanol. Then, crack generation as eliminated byusing fluorescent penetrant inspection every 100 hours. The results andthe chemical compositions of the conjunction glasses are shown in Table4.

                  TABLE 4                                                         ______________________________________                                               Chemical composition                                                                             Crack                                                      (wt %)             generation                                          Specimen No.                                                                           SiO.sub.2                                                                            Na.sub.2 O                                                                            B.sub.2 O.sub.3                                                                    Al.sub.2 O.sub.3                                                                    MgO  time (hr)                             ______________________________________                                        present                                                                       invention                                                                      1       64.0   5.0     13.0 13.0  5.0    500                                  2       60.0   5.0     17.0 13.0  5.0    800                                  3       50.0   5.0     27.0 13.0  5.0   1000                                  4       40.0   3.0     33.0 19.0  5.0  >2000                                  5       30.0   3.0     39.5 20.0  7.5  >2000                                  6       20.0   5.0     47.0 20.0  7.5  >2000                                  7       10.0   8.0     50.0 25.0  7.0    600                                  8       32.0   4.5     37.0 19.0  7.5  >2000                                  9       36.0   4.5     33.0 21.0  5.5  >2000                                 10       35.0   9.0     34.0 16.0  6.0   1700                                 11       32.0   3.0     33.0 29.0  3.0   1200                                 12       34.0   3.0     35.0 24.0  4.0  >2000                                 13       34.0   3.0     38.0 16.0  9.0  >2000                                 14       34.0   3.0     38.0 16.0  9.0  >2000                                 15       38.0   3.0     41.0 13.0  5.0   1600                                 16       35.0   4.0     30.0 12.0  19.0  1600                                 17       34.0   18.0    30.0 13.0  5.0   1100                                 Comparative                                                                   example                                                                       18       67.0   4.0     19.0  7.0  3.0  crack                                                                         generation                                                                    during                                                                        connection                            19       30.0   4.5     30.0 32.0  3.5  crack                                                                         generation                                                                    during                                                                        connection                            20       35.0   4.0     28.0 10.0  23.0 crack                                                                         generation                                                                    during                                                                        connection                            21       32.0   22.0    30.0 11.0  5.0  crack                                                                         generation                                                                    during                                                                        connection                            ______________________________________                                    

From the results shown in Table 4, it is understood that specimen Nos.1˜17 of the fourth aspect of the invention show good anti-corrosionproperties since cracks are not generated at least for 400 hours, butspecimen Nos. 18˜21 of the comparative example experience cracks whenthe connection operation is performed The reason for the crackgeneration during the connection operation is that a thermal expansioncoefficient of the glass is not equal to that of the beta or alphaalumina.

EXAMPLE 7

A charge-discharge test was performed with respect to a NaS cell usingthe glass joint body of the fourth aspect of the invention. That is tosay, with respect to the sodium-sulfur cells wherein the beta aluminatube and the insulator made of alpha alumina are connected as shown inFIG. 1 by using glasses of specimen Nos. 1˜17 in example 6, thecharge-discharge test was performed under a temperature of 350° C. and acurrent density of 150 mA/cm². As a result, all the sodium-sulfur cellsendured at least 1000 cycles.

EXAMPLE 8

With respect to specimen Nos. 4˜6, 8, 9, 12˜18 among the glass jointspecimens in example 6, a temperature ascent and descent test from roomtemperature to 350° C. was performed under N₂ atmosphere, and a crackgeneration of the connection portion was examined every 5 times. As aresult, all of the specimens showed no crack generation after 10repeated tests. Moreover, specimen Nos. 4, 6, 12, 13, 14 show a smallcrack generation after 15 tests, and specimen Nos. 5, 8, 9 show no crackgeneration even after 30 tests.

As mentioned above, according to the invention, since ceramics andceramics are connected with each other by using a glass having apredetermined chemical composition, a durability against sodiumcorrosion of the glass joint body can be improved. Therefore, if thepresent invention is applied to the glass joint body used in a hightemperature type secondary cell such as a sodium-sulfur cell or AlkaliMetal Thermo-Electric Converter, life of the apparatus can be increased.

What is claimed is:
 1. A glass joint body comprising a first ceramicmember and a second ceramic member connected by a glass consisting of10˜64 wt % of SiO₂, 3˜30 wt % of Na₂ O, at least 2 wt % Al₂ O₃ and thebalance of B₂ O₃.
 2. A glass joint body according to claim 1, whereinsaid first and second ceramic members are a beta alumina member and aninsulation ceramic member is a high temperature secondary cell or in analkali Metal Thermo-Electric Converter.
 3. A glass joint body comprisinga first ceramic member and a second ceramic member connected by a glassconsisting of 10˜64 wt % of SiO₂, 3˜20 wt % of Na₂ O, 12˜30 wt % of Al₂O₃, 20 wt % or less of MgO, and the balance of B₂ O₃.
 4. A glass jointbody according to claim 3, wherein said first and second ceramic membersare a beta alumina member and an insulation ceramic member in a hightemperature secondary cell or in an Alkali Metal Thermo-ElectricConverter.